First of all, I fear that with the planned "upconversion" of VHS tape to 1080p you would not gain anything. VHS comes in 480i or 576i, depending on it being NTSC or PAL format (if you're in the U.S. it's pretty much guaranteed NTSC and 480i).
What matters most in these cases is that you get the content with as few as possible errors off the tape onto digital media, which your Toshiba can probably do best as these units have usually a pretty okay error correction. So, VHS->DVD in 480i (if the tape is NTSC) or 576i (if the tape is PAL) on the Toshiba will get you probably the best result. In that resolution you should also fit a long movie onto a DVD, or you split it up across multiple DVDs... on the Mac you can put it back together, e.g. with iMovie.
Next, you could scale the movie up by converting it to "something HD", like 720p or even 1080p with some converter app, but the result will very much depend on the converter's scaling capability and quality, and likely look pretty bad on your HD TV.
Modern TVs are actually pretty good with scaling (see pictures coming in on "regular" TV channels), so I'd expect you to find that leaving the resolution where it is will look by far best on any TV.
Doesn't rule out some editing for color, contrast, and of course, the titles and cuts as usual for home movies...
I wasn't sure if I would gain anything by skipping the initial conversion to DVD and import directly into imovie as opposed to copy to DVD, convert .vob filed to mpeg2 and then import to imovie. I presume, now, that all these conversions take place before they get into imovie regardless. I also suspected I would still need a video capture device between the VCR and the imac anyway. It was the HDMI out on the DVD/VCR that piqued my curiosity in terms of a direct input into the imac.
Thanks so much for your help....Karl
I also suspected I would still need a video capture device between the VCR and the imac anyway.
I understand you have a VCR/DVD combo enabling you to copy from VHS tape to DVD media. Well, then you should be able to do so without a video grabber: Put the DVD into your iMac and use a (free) software converter to make it any format you want within its abilities.
Advantage: Free, no extra gear required, and probably a decent result due to a probably decent error correction in the VCR/DVD unit. Disadvantage: Two conversions required, result depending also on the quality of the software converter running on the iMac.
Alternatively, use a video grabber via the analog output of the VCR.
Advantage: Only one conversion process, assuming that the grabber software produces the movie file format you prefer. Disadvantage: Image quality depending on the analog VCR output and the conversionof the grabber and its software.
Frankly, the affordable video grabbers aren't that famous for their picture quality. So, as already indicated, in every aspect you might be better off by using the equipment you already have.
Just keep your expectations low as far as upscaling to HD is concerned, the good old GIGO rule is true here, too: Garbage In, Garbage Out...